Reflective ultra-wide field fundus imager

ABSTRACT

Improved scanning ophthalmoscopes for scanning the retina of an eye are discussed in the present disclosure. One example scanning ophthalmoscope includes an uncollimated light source, a first scanning element, a second scanning element, a slit of a first aspherical mirror, and a second aspherical mirror. The uncollimated light source produces a beam of light to illuminate the retina. The beam of light is relayed from the first scanning element onto the second scanning element by the slit of the first aspherical mirror. The second aspherical mirror relays the beam of light from the second scanning element to the pupil of the eye.

PRIORITY

The present application is a divisional application of U.S. patentapplication Ser. No. 15/415,116, filed on Jan. 25, 2017, which claimspriority to U.S. Provisional Application Ser. No. 62/293,068, filed Feb.9, 2016, the contents of each of which are hereby incorporated byreference.

BACKGROUND

The present invention relates to improved scanning ophthalmoscopes forscanning the retina of an eye.

Some of the previous scanning ophthalmoscopes are described by U.S. Pat.Nos. 5,815,242 and 7,959,290, and US Publication No. 2013/0093996, eachof which is hereby incorporated by reference. In particular, U.S. Pat.No. 5,815,242 describes a scanning laser ophthalmoscope which producesimages of the rear surface of the human eye, and particularly of theretina, by utilizing an aspherical mirror to reflect light beams,produced by multiple scanning laser light sources, into the retina. Thescanning laser ophthalmoscope comprises a laser light source, a firstscanning system, a second scanning system, and an aspherical mirror. Thelaser light source, the first scanning system, and the second scanningsystem are adapted to combine to provide a two-dimensional laser lightscan from an apparent point source. The aspherical mirror has two fociand is adapted to transfer the two-dimensional laser light scan from theapparent point source into the eye. The scanning laser ophthalmoscope isadapted to provide the apparent point source at a first focus of theaspherical mirror and to accommodate the eye at a second focus of themirror.

U.S. Pat. No. 7,959,290 describes a scanning ophthalmoscope for scanningthe retina of an eye comprising a source of collimated light, a firstscanning element, a second scanning element, a scan compensation device,and a scan transfer device. The first scanning element produces aone-dimensional collimated light scan in a first direction. The scancompensation device delivers the one-dimensional collimated light scanfrom the first scanning element onto the second scanning element in amanner that the scan in the first direction appears to be provided froman apparent point source. The second scanning element produces from theone-dimensional collimated light scan a two-dimensional collimated lightscan by scanning in a second direction from the apparent point source.The scan transfer device transfers the two-dimensional collimated lightscan from the apparent point source into the eye.

US Publication No. 2013/0093996 describes a scanning ophthalmoscope forscanning the retina of an eye and a method of scanning the retina of aneye. The ophthalmoscope comprises a source of collimated light, a firstscanning element, a second scanning element, a scan relay device, and ascan transfer device. The source of collimated light, the first andsecond scanning elements, and the scan relay device combine to provide atwo-dimensional collimated light scan from an apparent point source. Thescan transfer device transfers the two-dimensional collimated light scanfrom the apparent point source into the eye.

Here we describe further improved scanning ophthalmoscopes and/orapparatuses, which are capable of not only performing point scanning ofthe retina but also, in some embodiments, the line scanning of theretina.

SUMMARY

According to one aspect of the subject matter described in the presentapplication, a scanning ophthalmoscope for scanning the retina of an eyecomprises an uncollimated light source for producing a beam of light toilluminate the retina; a first scanning element; a second scanningelement; a slit of a first aspherical mirror, wherein the beam of lightfrom the first scanning element is relayed onto the second scanningelement by the slit of the first aspherical mirror; and a secondaspherical mirror for relaying the beam of light from the secondscanning element to the pupil of the eye.

According to another aspect of the subject matter described in thepresent application, a scanning ophthalmoscope for scanning the retinaof an eye comprises a light source for producing a beam of light toilluminate a line on the retina; a pupil splitting element forseparating light illuminating the retina and light returning from theretina; a scanning element; a slit of a first aspherical mirror forrelaying light from the pupil splitting element onto the scanningelement to provide a scanning line; and a second aspherical mirror fortransferring the scanning line from the scanning element into the pupilof the eye.

According to yet another aspect of the subject matter described in thepresent application, a scanning ophthalmoscope for scanning the retinaof an eye through the pupil comprises a light source for illuminatingthe retina with one or more rays of light; at least one asphericalmirror having astigmatism; a first scanning element; and a secondscanning element, wherein the first scanning element and the secondscanning element are placed in a way such that (a) a ray of light whenincident on the first scanning element travels to the second scanningelement without being reflected by the aspherical mirror, and (b) thepupil is imaged to the first scanning element for rays travelling in afirst plane defined by the direction of astigmatism and optical axis,and the pupil is imaged to the second scanning element for light raystravelling in the plane perpendicular to the first plane.

It should be noted that the various scanning ophthalmoscopes discussedin the present disclosure are not limited to use with elliptical mirrorsand slits of the elliptical mirrors, and that aspherical mirrors andslits of the aspherical mirrors are also possible for use with theseophthalmoscopes and are within the scope of the present invention.

It should further be noted that the terms “slit elliptical mirror” and“elliptical mirror” are used throughout this disclosure to refer to twodifferent sizes of an elliptical mirror. An elliptical mirror is aportion of an elliptical surface with a normal elliptical, circular, orrectangular clear aperture. The term “slit elliptical mirror” or “slitof an elliptical mirror” refers to a part/portion of the ellipticalmirror with a relatively large width to height ratio (e.g., 5:1 or 10:1)that can be used for relaying light from one element to another. Theseterminologies are further clearly demonstrated in FIGS. 3A and 3B, wherereference numeral 302 represents an elliptical mirror 302 and referencenumerals 104 a or 104 b represents a slit of the elliptical mirror 302.

Furthermore, it should be understood that the language used in thespecification has been principally selected for readability andinstructional purposes and not to limit the scope of the inventivesubject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a side view of a point scanning ophthalmoscope thatis capable of performing a point scan of the retina of an eye. FIG. 1Billustrates a side view of a line scanning ophthalmoscope that iscapable of performing a line scan of the retina. FIGS. 1C and 1Dillustrate a front view and a 45 degree angle view of the point or linescanning ophthalmoscope, respectively.

FIGS. 2A and 2B illustrate a top view and a side view of a slit of anelliptical mirror (shown in FIGS. 1A-1C) and scanners arranged at itstwo focus points, respectively.

FIG. 3A illustrates an example off-axis arrangement of the slit. FIG. 3Billustrates an example on-axis arrangement of the slit.

FIG. 4A illustrates a 45 degree angle view of an alternative line scanophthalmoscope that is capable of performing line scanning of the retinaof an eye using a slit and an elliptical mirror. FIGS. 4B and 4Cillustrate a front view and a side view of the line scan ophthalmoscope,respectively.

FIG. 5A illustrates a side view of a point scan ophthalmoscope that iscapable of performing point scanning of the retina of an eye using twoelliptical mirrors. FIG. 5B shows arrangement of two scanners orscanning elements placed next to each other without optical relaybetween them. FIG. 5C illustrates footprint of scanning beam on thepupil based on such an arrangement of the two scanners or scanningelements. FIGS. 5D and 5E illustrate a front view and a 45 degree angleview of the point scan ophthalmoscope, respectively.

FIGS. 6A-6C illustrate a side view, a front view, and a 45 degree angleview, respectively, of an alternative point scan ophthalmoscope that iscapable of performing point scanning of the retina of an eye using oneelliptical mirror.

DETAILED DESCRIPTION

All patent and non-patent references cited within this specification areherein incorporated by reference in their entirety to the same extent asif the disclosure of each individual patent and non-patient referencewas specifically and individually indicated to be incorporated byreference in its entirely.

Various point and line scanning ophthalmoscopes are now discussed indetail below with references to the figures. It should be noted thateven though all these ophthalmoscopes are discussed and shown for usewith an elliptical mirror and/or slit of an elliptical mirror, since anelliptical mirror is just one type of aspheric mirror, each of theseophthalmoscopes can be generalized to function with an aspheric mirrorand/or a slit of an aspheric mirror as well.

Point Scanning Ophthalmoscope

FIG. 1A illustrates a side view of a general point scan ophthalmoscope100 that is capable of performing a point scan of the retina of an eye.Point scanning of the retina means scanning the retina point by pointover two dimensions and the image of the retina is reconstructed basedon the scanned points. As depicted, the scanning ophthalmoscope system100 comprises a source of light 101, a first scanner or scanning element102, a pupil splitter 103, a slit 104 of an elliptical mirror (referredto herein as a slit elliptical mirror 104), a second scanner or scanningelement 106, an elliptical mirror 108, a detector 112, a processor 114,and a display 116. As mentioned earlier, the slit 104 could begeneralized to be a slit of an aspherical mirror and the ellipticalmirror 108 could be an aspherical mirror.

The source of light 101 used in the scanning ophthalmoscope can beeither a collimated light source or an uncollimated light source. It isadvantageous to use an uncollimated light source for obtaining sharpretinal images. For a given eye, the degree of convergence or divergenceof the light beam needs to vary depending on the point of the retinathat is scanned. By using the uncollimated light source, the range ofconvergence or divergence is adjustable for eyes with differentrefractive error. In some embodiments, the source of light 101 used inthe scanning ophthalmoscope may be a laser producing a laser beam, whichis incident on the first scanning element 102 via the pupil splitter103. The pupil splitter or splitting element 103 may be any element thatseparates light illuminating the retina from light that is returningfrom the retina.

For example, the pupil splitting element can be an optical element withtwo parts, where one part is reflective for illumination purposes andthe other part is transmissive for observation purposes. The firstscanning element 102 can be a high speed rotating polygon mirror and thesecond scanning element 106 can be a slow speed oscillating plane mirroror vice versa. The slit elliptical mirror 104 has two foci and the twoscanning elements 102 and 106 are located at the two foci of the mirror104. For instance, the first scanning element 102 is located at thefirst focus of the mirror 104 and the second scanning element 106 islocated at the second focus of the mirror 104, as shown for example inFIGS. 2A, 2B, and 3A. In some embodiments, the positioning of the twoscanning elements 102 and 106 at the two focus points of the mirror 104depends on whether the mirror is on-axis or off-axis. For instance, ifthe mirror is off-axis, then the two scanning elements 102 and 106 arelocated at the two focus points of the mirror (for example, see FIG.3A). Whereas, if the mirror is on-axis, then the two scanning elements102 and 106 are located off the two focus points of the mirror (forexample, see FIG. 3B). This is further discussed below with respect toFIGS. 3A and 3B.

The first scanning element 102 and the second scanning element 106 areeach capable of generating one dimensional light scan(s) of the laserbeam in a particular direction (e.g., vertical, horizontal, etc.). Thefirst scanning element 102 and the second scanning element 106 thustogether create a two-dimensional light scan in the form of a rasterscan pattern. For instance, the first scanning element 102 produces aone-dimensional light scan in a first direction (e.g., vertical) when alight beam from the light source (not shown) is incident on the firstscanning element 102. The one-dimensional light scan then travels to thesecond scanning element 106 by the slit elliptical mirror 104 where theyare combined with a one-dimensional light scan produced by the secondscanning element 106 in a second direction (e.g., horizontal) to createthe two dimensional light scan.

The elliptical mirror 108 also has two foci. The second scanning element106 is located at the first focus of the mirror 108 and a subject's eye110 is located at the second focus of the mirror 108. The ellipticalmirror 108 and the second scanning element 106 are arranged such thatthe rotational axis of the second scanning element 106 is substantiallyperpendicular to the line joining the two foci of the elliptical mirror108. The elliptical mirror 108 projects the two dimensional scanprovided by the second scanning element 106 onto the subject's eye 110for scanning the retina. A beam reflected from the retina of thesubject's eye 110 is conveyed back through the scanning ophthalmoscopeand directed onto the detector 112 via pupil splitter 103. The collectedlight is sent to the processor 114, which is used to produce an image ofthe subject's retina. The resulting image can be displayed on thedisplay 116 or stored in memory for future reference and processing.

The slit elliptical mirror 104 described herein serves two importantfunctions. A first function of the mirror 104 is that of a scan transferof the laser beam from the first scanning element 102 to the secondscanning element 106. This function of the slit elliptical mirror 104 ismore clearly illustrated in FIGS. 2A and 2B that show a top view and aside view arrangement of the mirror 104 relative to the two scanningelements 102 and 106, respectively. The mirror 104 provides point topoint transfer, without introducing any translational component, whichwould cause failure of the laser beam to enter through the pupil of thesubject's eye 110. Thus, the laser beam appears to come from an apparentpoint source. A second function of the mirror 104 is that of a scanangle amplifier (see for example, U.S. Pat. No. 7,959,290).

Line Scanning Ophthalmoscope

FIG. 1B illustrates a side view of a general line scanningophthalmoscope 120 that is capable of performing a line scan of theretina. Line scanning of the retina means scanning a line or a long slitover the retina and the image of the retina is reconstructed based onthe scanned lines. In the line scan configuration, the arrangement ofthe elements 104, 106, and 108 remains the same as discussed above butnow the first scanning element 102 is replaced with the pupil splittingelement 103. So instead of requiring two scanning elements as in thecase of point scanning of the retina, a pupil splitting element and ascanning element are used for the line scanning of the retina. Therotational axis of the scanning element 106 is substantiallyperpendicular to the line joining the two foci of the elliptical mirror108 in slit elliptical mirror 104.

In the line scanning configuration, the pupil splitting element 103, thescanning element 106, and the pupil of the subject's eye 110 areoptically conjugate to each other and serve as a pupil stop of thesystem. Through a lens, all light from the line/slit source (not shown)will pass through the pupil splitting element 103 and form a fan oflight beams. The fan of light beams are reflected by the slit ellipticalmirror 104 and conveyed to the scanning element 106, which is thenconveyed to the elliptical mirror 108 and finally to the pupil of thesubject's eye 110 to form an illuminated line/slit on the retina. Thelight which is scattered from the illuminated retina of the subject'seye 110 is conveyed back through the same optical path to the pupilsplitting element 103, the detector 112, and the processor 114, which isused to produce a line/slit image of the subject's retina that can bedisplayed via the display 116. When the scanning element 106 scans, theilluminated line/slit on the retina of the subject's eye 110 will scanacross the retina and a full ultra-wide field image of the retina can bereconstructed.

Similar to the functions of the slit elliptical mirror 104 discussedabove with respect to the point scanning of the retina, in the linescanning embodiment, the mirror 104 serves as 1) the scan transferfunction from the pupil splitting element 103 to the scanning element106 and 2) the scan angle amplifier function.

FIGS. 1C and 1D illustrate a front view and a 45 degree angle view ofeither the general point scanning ophthalmoscope 100 or line scanningophthalmoscope 120, respectively.

FIGS. 3A and 3B illustrate two different arrangements of the slitelliptical mirror 104 that is discussed above with respect to FIGS.1A-1D and FIGS. 2A and 2B. It should be recognized that FIGS. 3A and 3Bas well as the other figures used to illustrate an implementation, anindication of a letter after a reference number or numeral, for example,“104 a” is a specific reference to an element or component that isdesignated by that particular reference numeral. In the event areference numeral appears in the text without a letter following it, forexample, “104,” it should be recognized that such is a general referenceto different implementations of the element or component bearing thatgeneral reference numeral. By way of example, 104 is generally referringto the slit elliptical mirror shown in FIGS. 1A-1D and other figureswhile 104 a or 104 b in FIGS. 3A and 3B are referring to the twospecific cases when the slit elliptical mirror 104 is positionedoff-axis and on-axis, respectively.

In particular, FIG. 3A illustrates an off-axis arrangement of the slitelliptical mirror 104. Reference numeral 302 represents an exampleelliptical mirror and reference numerals 104 a represents a slit of theelliptical mirror 302 which is located off-axis to the mirror axis 304.Reference numerals 306 and 308 indicate the two focus positions of themirror 302. As depicted in FIG. 3A, when the slit is off-axis (indicatedby reference numeral 104 a), the two scanning elements 102 and 106 arelocated at the focus positions of the mirror 302. The components 104 a,102, and 106 are arranged such that when the light hits the off-axisslit 104 a, the scanning element 106 doesn't block light from the firstscanning element 102.

Referring now to FIG. 3B, when the slit is on-axis (indicated byreference numeral 104 b), the two scanning elements 102 and 106 areoffset from the two focus positions 306 and 308 but are located near tothese positions. Here also the components 104 b, 102, and 106 arearranged such that when the light hits the on-axis slit 104 b, thescanning element 106 doesn't block light from the first scanning element102.

Line Scanning Ophthalmoscope with Two Elliptical Mirrors

FIG. 4A illustrates a 45 degree angle view of an alternative line scanophthalmoscope 400 that is capable of performing line scanning of theretina of an eye 110 using a slit and an elliptical mirror. As mentionedelsewhere herein, the slit could be a slit of an aspherical mirror andthe instead of elliptical mirror it could be an aspherical mirror. Theline scan ophthalmoscope 400 comprises a source ofcollimated/uncollimated light, such as the source 101 (not shown), apupil splitting element 103, a slit elliptical mirror 104, a scanningelement 106, and an elliptical mirror 108. Although not shown, it shouldbe understood that the line scan ophthalmoscope 400 also includes thedetector 112, the processor 114, and the display 116. Note that likewisenumerals are used to refer to the same or similar elements/components,which were discussed above with respect to at least FIG. 1B. Also notethat these elements/components perform the line scanning of the retinain the same way as discussed above with respect to at least FIG. 1B andhence, the description will not be repeated here.

The line scan ophthalmoscope discussed herein with respect to FIGS.4A-4C is different from the line scan ophthalmoscope discussed abovewith respect to FIGS. 1B in the way that one or more of the components103, 104, 106, and 108 are arranged. For instance, here the rotationalaxis of the scanning element 106 is substantially parallel to the linejoining the two foci of the elliptical mirror 108. The advantage of suchan arrangement depicted in FIGS. 4A-4C is that the angular distortion inthe vertical direction can be cancelled out if the two ellipticalmirrors 104 and 108 are designed properly.

FIGS. 4B and 4C illustrate alternate views of this line scanophthalmoscope. In particular, FIG. 4B shows a front view and FIG. 4Cshows a side view.

Point Scanning Ophthalmoscope with Two Elliptical Mirrors/One EllipticalMirror

FIG. 5A illustrates a side view of a point scan ophthalmoscope 500 thatis capable of performing point scanning of the retina of an eye 110using two elliptical mirrors. The point scan ophthalmoscope 500comprises a source of collimated/uncollimated light, such as the source101 (not shown), two scanning elements 102 and 106, a first ellipticalmirror 504, and a second elliptical mirror 108. The two ellipticalmirrors 504 and 108 are arranged such that they cancel out the angulardistortion along the long axis of these mirrors. Although not shown, itshould be understood that the point scan ophthalmoscope 500 alsoincludes the detector 112, the processor 114, and the display 116. Notethat likewise numerals are used to refer to the same or similarelements/components, which were discussed above with respect to at leastFIG. 1A and FIGS. 4A-4C. Also note that these elements/componentsperform the point scanning of the retina in the same way as discussedabove with respect to at least FIG. 1A and hence, the description willnot be repeated here.

The point scan ophthalmoscope 500 discussed herein with respect to FIGS.5A-5E is different from point line scan ophthalmoscope 100 discussedabove with respect to FIG. 1A in the way that the two scanning elements102 and 106 are arranged. For instance, the two scanning elements 102and 106 are placed next to each other with a certain defined distance(see FIG. 5B) without optical relay between them (i.e., lighttransmission from one scanning element to another is direct and is notcarried out by a mirror in between them). The advantage of placing thetwo scanning elements this way is that 1) no beam pre-positioning isnecessary, 2) no optical relay is necessary, 3) without beampre-positioning and optical relay, the system can be more compact andcost effective, and 4) one or two elliptical mirrors having astigmatismcan be used to image the two scanning elements 102 and 106 to the samespot of the pupil of the subject's eye 110. This is further illustratedin FIG. 5C that shows an example footprint of the scanning beam on thepupil (indicated by reference numeral 510) formed based on such anarrangement of the two scanning elements.

FIGS. 5D and 5E illustrate alternate views of this point scanophthalmoscope. In particular, FIG. 5D shows a front view and FIG. 5Eshows a 45 degree angle view.

In some embodiments, the point scanning as discussed with respect toFIGS. 5A-5E is also possible with only one elliptical mirror. FIGS.6A-6C illustrate a side view, a front view, and a 45 degree angle view,respectively, of a point scan ophthalmoscope that is capable ofperforming point scanning of the retina of an eye using one ellipticalmirror 504. It should be understood that with only one elliptical mirror504, there will be angular distortion along the long axis of theelliptical mirror 504.

As discussed elsewhere herein, the embodiments discussed with referenceto FIGS. 5A-5E and 6A-6C can be generalized to function with asphericalmirrors and slits of aspherical mirrors and are within the scope of thepresent disclosure.

In the above description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofthe specification. It should be apparent, however, that the subjectmatter of the present application can be practiced without thesespecific details. It should be understood that the reference in thespecification to “one embodiment”, “some embodiments”, or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin one or more embodiments of the description. The appearances of thephrase “in one embodiment” or “in some embodiments” in various places inthe specification are not necessarily all referring to the sameembodiment(s).

The foregoing description of the embodiments of the present subjectmatter has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit the presentembodiment of subject matter to the precise form disclosed. Manymodifications and variations are possible in light of the aboveteaching. It is intended that the scope of the present embodiment ofsubject matter be limited not by this detailed description, but ratherby the claims of this application. As will be understood by thosefamiliar with the art, the present subject matter may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof.

1. A scanning ophthalmoscope for scanning the retina of an eye, saidophthalmoscope comprising: an uncollimated light source for producing abeam of light to illuminate the retina; a first scanning element; asecond scanning element; a slit of a first aspherical mirror, whereinthe beam of light from the first scanning element is relayed onto thesecond scanning element by the slit of the first aspherical mirror; anda second aspherical mirror for relaying the beam of light from thesecond scanning element to the pupil of the eye.
 2. The scanningophthalmoscope as recited in claim 1, wherein the first and/or thesecond aspherical mirrors are elliptical mirrors.
 3. The scanningophthalmoscope as recited in claim 2, wherein said ophthalmoscopeperforms point scanning of the retina.
 4. The scanning ophthalmoscope asrecited in claim 2, wherein the slit is positioned off-axis relative tothe first aspherical mirror.
 5. The scanning ophthalmoscope as recitedin claim 2, wherein the slit is positioned on-axis relative to the firstaspherical mirror.
 6. The scanning ophthalmoscope as recited in claim 2,wherein the second aspherical mirror has two foci and the rotationalaxis of the second scanning element is substantially perpendicular to aline joining the two foci of the second aspherical mirror.
 7. Thescanning ophthalmoscope as recited in claim 2, wherein the slit of thefirst aspherical mirror functions as a relay component for relaying thelight from the first scanning element to the second scanning element andas a scan angle amplifier.
 8. A scanning ophthalmoscope for scanning theretina of an eye, said ophthalmoscope comprising: a light source forproducing a beam of light to illuminate a line on the retina; a pupilsplitting element for separating light illuminating the retina and lightreturning from the retina; a scanning element; a slit of a firstaspherical mirror for relaying light from the pupil splitting elementonto the scanning element to provide a scanning line; and a secondaspherical mirror for transferring the scanning line from the scanningelement into the pupil of the eye.
 9. The scanning ophthalmoscope asrecited in claim 8, wherein the first and/or the second asphericalmirrors are elliptical mirrors.
 10. The scanning ophthalmoscope asrecited in claim 9, wherein the second aspherical mirror has two fociand the rotational axis of the scanning element is substantiallyparallel to a line joining the two foci of the second aspherical mirror.11. The scanning ophthalmoscope as recited in claim 9, wherein the slitof the first aspherical mirror functions as a relay component forrelaying the light from the pupil splitting element to the scanningelement and as a scan angle amplifier.
 12. The scanning ophthalmoscopeas recited in claim 9, wherein the scanning element comprises a rotatingor an oscillating mirror.